Oil storage method

ABSTRACT

Vessels for the storage of liquid, such as crude oil, are formed by detonating a nuclear (or conventional) explosive under the surface of a permafrost area such as occurs in arctic and subarctic regions, to form an open crater. The walls of such a crater are naturally sealed or may be easily sealed liquidtight by the freezing of water in the pore spaces of the host media, whereby oil (or other product) may be stored in the permafrosted crater without seepage loss. Further, permafrost (or frozen moisture between the permafrost and the product to be stored) in the fallback material (rubble) in the crater will form an effective separation barrier between the oil (or other product) and residual radioactivity formed as a result of the nuclear detonation.

i1 iiiieei mites mm Hague Feb. 212, 11972 [54] (NHL STORAGE METHUID pages B- 32 to B- 34, Vol. 31 [72] Inventor: Richard S. iilague, Boulder City, Nev. I and Gas Journal Sept 1968 pages 90 92 66 [73] Assignee: The United States oi America as represented by the Atomic Energy tCom- Primary Examiner-Peter M. Caun mission Att0rneyRoland A. Anderson [21] Appl' 34:]59 Vessels for the storage of liquid, such as crude oil, are formed by detonating a nuclear (or conventional) explosive under the [52] US. Ci. ..6l/.5, 61/36 A, 61/53.54 Surface of a Permafrost area Such as occurs in arctic and [51] time! ..B65g slot) arctic g to form an p crater. The walls of such a [58] Field oi Search ..6i/.5, 36, 53.54; 166/247, Crater ar naturally Sealed or may be easily sealed liquidtight 166/916 1 by the freezing of water in the pore spaces of the host media,

whereby oil (or other product) may be stored in the per- [56] Referen es Cited mafrosted crater without seepage loss. lFurther, permafrost (or frozen moisture between the permafrost and the product to be NY ED STATES PATENTS stored) in the fallback material (rubble) in the crater will form an effective separation barrier between the oil (or other 3,159,006 12/1964 Shepcevich ..6l/.5 X p and residual radioactivity folrmed as a result of the OTHER PUBLICATIONS nuclear detonation.

The Petroleum Engineer, August 1959 by Roland H. Carlson, ll Claim, 2 Drawing Figures A \Y, A Y A /W PAIENIEmB22|m2 3,643,441

AVAWAYNA Y A (WW/6% 1 I v v I I,

Fig. 2

IN VIi'N'I'OR. Richard S. Hague BY K,.. 4 W

ATTORNEY.

on srotmcn METHOD BACKGROUND OF THE INVENTION The invention disclosed herein was made in the course of work performed by the United States Atomic Energy Commission.

With the development of large oil fields in arctic and subarctic regions, severe problems are posed in providing for the economic movement of the extracted crude oil to existing refining facilities and markets without detrimenting the rate of oil production. For example, the Prudhoe Bay discovery on the north slope of Alaska has a huge productivity projection estimated at 500,000 bbl. of oil per day. In order that full production of oil may be maintained, the oil must be shipped from the field on a substantially continuous basis, or stored until such time that large volume shipments can be made. Substantially continuous shipment may be accomplished by pipeline or by railroad tank cars and even then considerable storage would be required at the makeup point. The arctic environment of the region poses difficult problems in the construction of railroads or pipelines rendering same extremely costly. In particular, the permafrost, i.e., permanently frozen ground extending to depths of as much as 2,500 ft., is prevalent in the region and present unique problems not encountered in other climate environments. The first 18 to 24 ft. of the permafrost is an active layer which thaws in the summer and turns to a gooey mass unless suitably insulated, such as by covering with a 7-foot-deep layer of gravel. Consequently, for the construction ofa railroad or pipeline, rather elaborate and expensive measures would be required to anchor the structure to a stable region of the permafrost not subject to thawing. The large total number miles of a railroad or pipeline required to reach refining facilities and markets would be an added factor to the high construction costs. Cost estimates have ranged from 350 million dollars for a 700-mile pipeline to the south coast of Alaska to 1.5 billion dollars for a 3,000-mile pipeline to the midwest.

From an environmental standpoint, the construction of a long pipeline or railroad would scar and disrupt the surface as well as form a manmade separation barrier across hundreds of miles of nearly virgin arctic and subarctic terrain. Just what effect this would have on the migration, etc., of plants and wildlife in the area would require extensive study.

By virtue of the foregoing problems, and the expense attending the construction of a railroad or pipeline, shipping of oil from Alaskas north slope by ocean tanker may well prove to be the most economical and environmentally acceptable expedient. This is supported by the recent successful trip of a large tanker, the Manhattan, which was modified to plow through ice up to feet thick while negotiating the Northwest Passage.

Oil fields must produce continuously and tankers must be filled rapidly to result in optimum economies. Therefore, in order for full oil production to be maintained, it is necessary that adequate storage facilities be provided between shipments. As annual production of 180 million bbl. is anticipated from Alaska's north slope, the construction of conventional oil storage facilities with such large capacity would be a formidable and very expensive undertaking, particularly in view of the added problems imposed by the arctic environment. Preliminary estimates indicate conventional storage would cost about five times as much to build on the north slope as in the lower 48. The economic benefits which may be derived from shipment by ocean tanker would be substantially offset by the cost of the necessary storage facilities where they are of a conventional nature.

Problems similar to those attending the economic ship of oil from Alaskas north slope will also be present with the discovery and development of substantial oil resources in other arctic regions, such as the north slope of Canada.

SUMMARY OF THE INVENTION The general object of the present invention is to simply and economically provide the storage of very large quantities of oil (or other products) in permafrost areas as exist in arctic and subarctic regions of the world. The storage facilities provided may, for example, be employed to permit maintenance of full production from oil fields in such regions by providing ample storage for oil between shipments, whether by ocean tankers, railroad cars or some other means.

In the accomplishment of the foregoing and other objects and advantages of the invention, there is provided an oil storage method which generally comprises detonating a nuclear explosive under the surface of' permafrost to form an open crater therein with frozen water in the pore spaces of the host media sealing the crater walls liquidtight and sealing residual radioactivity into the fallback material to render the crater contamination free. The impermeable, contamination free, storage vessel thus formed is then. filled with oil or other products. Seepage loss of oil and radioactive contamination is prevented by the sealed frozen surface of the crater. The oil effectively insulates such frozen surface to keep it sealed even during relatively warm months of the year. Should melting occur to minor depths during the warm season, permafrost below the melt zone would prevent lateral migration of the melt water which in turn would prevent migration of the stored oil (or other product).

BRIEF DESCRIPTION OF THE DRAWING The invention is illustrated in the accompany drawing, wherein:

FIG. 1 is a vertical section through a geological formation suited to the practice of the oil storage method of the present invention, depicting the emplacement of a nuclear (or conventional) explosive preliminary to the formation of an im permeable crater for oil storage; and

FIG. 2 is a view similar to FIG. I depicting the resulting crater as employed for the storage or" oil (or other product) in accordance with the method.

DETAILED DESCRIPTION OF THE INVENTION Considering now the invention in more detail, and referring to the illustrated form thereof in the accompanying drawing, there will be seen to be provided a method of economically storing tremendous volumes of crude oil in permafrost areas as exist in arctic and subarctic regions, such as the north slopes of Alaska and Canada where oil fields have been discovered which have a huge productivity projection. Generally, the existence of the permafrost and the general remoteness of the areas are considered to represent severe hindrances to conventional construction practices which might be undertaken, for example, to construct large capacity oil storage facilities such as tank farms." However, in accordance with the present invention, the properties of permafrost are utilized to good advantage to facilitate the relatively economical storage of huge quantities of oil in a unique manner. More particularly, a nuclear explosive 11 is detonated under the surface of the ground, within the permafrost 12 to form a crater 13 therein. In this regard, the ex plosive 11 is emplaced in the permafrost 12 at a depth of burst predetermined with respect to the yield of the explosive to form a crater 13 of desired capacity. Emplacement may be accomplished in a conventional manner as by drilling a shaft 14 in the permafrost to the predetermined depth of burst, lowering the explosive to the base of the shaft, and stemming the shaft. The depth of burst and yield of the explosive are selected relative to each other to form a throwout crater of design volume upon detonation of the explosive. Selection of appropriate relative parameters to form a crater of desired dimensions may be based upon well established nuclear explosive cratering criteria as set forth in the published literature, for example TID-7695, Engineering With Nuclear Explosives--Proeeedings of the Third Plowshare Symposium," Apr. 21, 22, 23, 1964, US. Atomic Energy Commission/Division of Technical Information, pages 51-74, and TEI857, Potential Application on Nuclear Explosives in Development and Management of Water ResourcesPrinciples, by Arthur M. Piper and Frank W. Stead, March 1965, U.S. Department of the Interior, Geological Survey, Washington, DC, pages 40-45.

It will be appreciated that to the extent described to this point, the crater 13 and formation thereof are conventional nuclear techniques. However, craters which have been formed heretofore have been formed in normal geological strato such as alluvium, basalt, and the like, and have been permeable to liquids. Consequently, such craters have been considered to be generally unsuited to the storage of valuable liquid, such as oil, where substantial seepage loss cannot be tolerated and where no effective system for separation between the product to be stored and residual radioactivity in the fallback material has been suggested.

In accordance with the particularly salient aspects of the present invention, the crater 13 formed in the permafrost 12 is unlike conventional craters heretofore formed in more normal geological strata, in that the crater walls are impermeable to the seepage ofliquids, and the permafrost locks up" or forms a separation barrier between the product to be stored and residual radioactivity in the fallback material, More particularly, the walls of the crater 13 are sealed liquidtight by frozen water in the pore spaces of the host media to thereby render same impermeable regardless of the actual permeability of the host medium. The crater walls and residual radioactivity are naturally sealed by the icing associated with the permafrost where the host medium contains sufficient moisture. In instances where the moisture is insufficient, or where additional moisture is required to lock up residual radioactivity moisture may be added as by flooding the rubble in the bottom of the crater and by sprinkling water on the crater walls during warm months to subsequently effect sealing to a sufficient depth upon freezing during the cold months. In any event, once the crater walls are frozen, the crater is filled with oil 17 or other products for storage without seepage loss. It is of importance to note that the oil 17, which has a lower freezing point than water, effectively insulates the frozen wall surface of the crater to maintain same sealed even during warm months when thawing of the active layer of the permafrost would be normally anticipated. Even if some thawing should take place, the permafrost below the melted zone would prevent migration of the melted water. As water and oil do not mix and as oil is lighter than water, the melted water then becomes the interface with the oil and the barrier to migration of the oil.

It will be appreciated that vaporization of the lighter fractions from the exposed surface of the oil 17 stored in the crater 13 is relatively low in an arctic or subarctic climate because of the low temperature. In the event that not even low-order vaporization loss can be tolerated, the loss may be eliminated or minimized by covering the surface of the stored oil with plastic film, foam, or other vapor-impervious covering material (not shown).

Considering now a specific example of the application of the oil storage method of the present invention, the Prudhoe Bay oil discovery on Alaskas north slope is currently estimated to have a projected productivity of at least 500,000 bbl. of oil per day. A crater formed in a permafrost by detonating a IOO-kiloton nuclear explosive emplaced at appropriate depth of burst (about 600 feet) has a volume of the order of 6.6x l 0 cubic yards. It is to be noted that the depth of burst is substantially less than the depth of the permafrost, which extends to as much as 2,500 feet on Alaskas north shore, whereby the crater is formed entirely in the permafrost. The volume of the sealed crater thus provided would facilitate the storage of over 30 million bbl. of oil. Consequently, six permafrost craters of this size, or one crater six times as large would provide a capacity sufficient for the storage of the entire annual production of million bbl. of oil, should this much storage be desired.

Delivery of 011 from a crater to ocean tankers could be very rapid, thus facilitating efficient use of time during whatever shipping season is proven practicable through the Northwest Passage.

Although the invention has been described hereinbefore with respect to specific steps of the method thereof, it will be appreciated that various changes and modifications may be made therein without departing from the true spirit and scope of the invention, and thus it is not intended to limit the invention except by the terms of the appended claims.

I claim:

1. An oil storage method comprising:

emplacing a nuclear explosive under the surface of permafrost and detonating said explosive to form an open throwout crater of design volume therein, said crater having fallback rubble material in the portion thereof; sprinkling water on the crater walls for subsequent freezing and flooding said fallback rubble material with water to seal said crater bottom and walls; and

filling said crater with oil whereby seepage loss and radioactive contamination of the oil is prevented by the sealed frozen walls of the crater and flooded rubble fallback material while the oil insulates said frozen walls to maintain same sealed.

no a 

1. An oil storage method comprising: emplacing a nuclear explosive under the surface of permafrost and detonating said explosive to form an open throwout crater of design volume therein, said crater having fallback rubble material in the portion thereof; sprinkling water on the crater walls for subsequent freezing and flooding said fallback rubble material with water to seal said crater bottom and walls; and filling said crater with oil whereby seepage loss and radioactive contamination of the oil is prevented by the sealed frozen walls of the crater and flooded rubble fallback material while the oil insulates said frozen walls to maintain same sealed. 